1. Field of the Invention
The present invention relates to a novel polyhydric phenol and an epoxy resin and an epoxy resin composition useful for encapsulating electronic devices derived from the polyhydric phenol as starting material.
2. Description of the Related Art
Recently, semiconductors such as LSI, IC, transistors and the like have been encapsulated by transfer molding with epoxy resins which are economically advantageous. Particularly, many of practical package have been recently mounted by surface mounting technology, so that immersion of them directly into a solder bath has been increasingly performed. During the immersion, the encapsulating materials are exposed to high temperatures of 200.degree. C. or more to cause expansion of the moisture which has been hygroscopically sorbed in the encapsulating materials. Therefore, the encapsulating materials become more prone to cracking.
For this reason, the epoxy encapsulating materials are required to have a resistance to cracking, especially much less hygroscopicity than the ordinary level thereof. Currently the most popular encapsulating materials are those using a glycidyl ether of o-cresol novolak, and packaged practically in moisture-proof wraps to be marketed and stored with moisture absorption being inhibited.
The encapsulating materials comprising a major component of glycidyl ether of o-cresol novolak are not only excellent in heat resistance, but also good to some extent in balance of heat resistance and less hygroscopicity. However, they are not necessarily satisfactory in such applications as a greater degree of less hygroscopicity being required as described above. Therefore, there has been desired an improvement of the encapsulating materials.
In addition, for example, cured products from difunctional epoxy resins such as glycidyl ether of bisphenol cyclohexane have an inferior thermal resistance as well as an insufficient curing property though they are excellent in less hygroscopicity.